In SharePoint v.2:
- Max # list items : 2000 (per folder level)
- Max lists per site : 2000 is a "reasonable" number
- Effect when we reach the limit : Exponential degradation of performance.
More info: http://technet.microsoft.com/en-us/library/cc287743.aspx
In SharePoint v.3:
- Max # list items : 2000 (per view, you can have million items as long as you don't display in a single view more than 2000 items)
- Max lists per site : 2000 is a "reasonable" number
- Effect when we reach the limit : Exponential degradation of performance when we enumerate more than 2000 items using the OM. An alternative is to use Search API or CAML queries.
More info: http://technet.microsoft.com/en-us/library/cc287790.aspx